Recombinant DNA methods developed since the late 1970s are now commonly employed as the primary means for producing pharmaceutical proteins for veterinary and human use. While recombinant methods have overcome many if not most of the challenges of producing these proteins, there are still problems to overcome regarding their formulation and administration.
Generally, proteins are thoroughly degraded by digestive processes and, as a rule, cannot be administered orally. They also generally are too large for transdermal administration. Furthermore, while many proteins can be prepared as liquid formulations, some at fairly high concentration, they are prone in the liquid state to physical and/or chemical degradation. In particular, aggregation is common in high concentration liquid protein formulations. Lyophilized formulations typically are much more stable. They do not undergo the degradation or aggregation that occurs in liquid formulations. Or if they do, the degradation or loss of protein activity occurs at a very much slower rate. However, it has been difficult or not possible to produce stable lyophilates of many therapeutic proteins that can be reconstituted in the concentrations necessary for therapeutic efficacy.
The problems associated with the formulation of protein therapeutics are especially challenging where high concentrations are desired, as in, for instance, formulations for subcutaneous administration. In fact, many proteins cannot be stably formulated in solution as high concentrations. And, even when proteins can be formulated, at least initially to high concentrations, often the formulations suffer from a variety of undesirable characteristics, such as poor shelf-life, poor or unreliable reconstitution, and unacceptable turbidity, foam, or bubbles upon reconstitution. As a result many protein therapeutics that might be advantageously administered subcutaneously have to be administered intravenously instead. Such problems are characteristic not only of proteins formulated entirely in liquid form, but also of proteins that have been lyophilized and must subsequently be reconstituted into a liquid form for administration.
Clearly there is a need for methods to produce and formulate protein therapeutic agents as stable lyophilates. In particular, there is a need for lyophilates that can be reconstituted to provide high concentration formulations. And in this regard, there is a need for lyophilates that can be reconstituted to high protein concentration formulations suitable for SC injection. One of the main obstacles to achieving such formulations is producing a purified, stable composition that can be reconstituted at the point of care in the high protein concentrations necessary for effective dosing via SC administration.
Obstacles to obtaining such formulations include: (i) uncontrolled and unpredictable protein instability during processing and storage, and loss of activity caused thereby; (ii) excessively long reconstitution times; (iii) unpredictable and uncontrolled formation of aggregates that deleteriously affect activity or result in unacceptable turbidity; (iv) foaming on reconstitution that decreases unit activity or is aesthetically unacceptable to users; (v) bubbling and effervescence that cause denaturation and decrease activity or are unacceptable to users; (vi) bubble entrapment that interferes with proper dosing; (vii) residual particulates that reduce recovery and dosing and/or are unacceptable to users; (viii) high viscosity that makes it difficult to properly load syringes for administration; and (ix) other uncontrollable deleterious alterations to bioactivity, bioavailability, reliability of dosing, or acceptability of dosing, that result from the formulation and reconstitution method.
Shire et al. have reviewed the opportunities and challenges of high concentration protein formulation in their review article, “Challenges in the Development of High Protein Concentration Formulations,” J. Pharm. Sci. 93(6): 1390-1402 (June 2004). Several workers have described approaches for improving highly concentrated protein formulations. Roser, in U.S. Pat. No. 4,891,319, describes the use of 0.05 and 25 weight percent trehalose to protect proteins against denaturation during drying. While the trehalose reduces loss of activity under some drying regimes, it does not solve many other of the aforementioned problems. Andya and co-workers, in U.S. Pat. No. 6,685,940, describe an antibody lyophilate made with a non-reducing sugar and histidine and antibody/sugar mole ratio of 100 to 600. Reportedly, the lyophilate could be reconstituted to an isotonic solution containing from 50 to 400 mg/ml antibody. Andya's process requires only one drying step, and often may not produce satisfactory results. While this has apparently proven effective for some antibodies, it has not proven to be generally applicable, and it does not overcome all of the aforementioned problems.
Rapp and Grandgeorge, in US Application Publication No. 2004/0005310 A1, describe methods for reconstituting lyophilized proteins under gas pressure between 1 mbar and atmospheric pressure, which are particularly suitable for blood coagulation proteins. The methods appear to advance the art marginally for some proteins. In particular, the innovation does not appear to be widely applicable and probably is not suitable for patient self-administration.
Thus, despite these and other improvements, there remains a need for improved methods for preparing and formulating highly concentrated proteins and for high concentration protein preparations that have a long shelf life, are stable under relatively unfavorable conditions (that may be encountered during shipping, storage, and use), can be reliably reconstituted, and conveniently administered in form and manner entirely acceptable to a wide variety of users. In particular, there is a need for reliable methods for formulating protein therapeutics in a manner that preserves activity, provides adequate stability to allow long-term storage, and provides reliable formulation at the point of care for high concentration protein formulations suitable for subcutaneous administration.